1. Field of the Invention
This invention relates to a new crank lever which, being extremely light and hence of low inertia although very strong, is particularly suitable for application to the dobby-heddle frame connection of modern looms which are required to operate at increasingly high speed.
2. Description of the Related Art
It is known that in transmitting the dobby commands to the heddle frames of a loom, a double series of crank levers is used in which the levers of each series are positioned adjacent to each other and are pivoted on the same shaft.
Said crank levers are currently constructed of steel or cast iron in one piece by forging or casting, and are therefore very heavy. In view of the current tendency towards increasingly high speed, it has been sought to lighten the moving members of the loom as much as possible, and in particular these crank levers.
However, constructing a crank lever of aluminum in one piece by casting, which would be expected to achieve the required lightness, would in this case not be possible as cast aluminum cannot be guaranteed to possess the necessary fatigue strength because of the possible presence of porosity in the cast material or of actual casting defects, such strength however being required because of the high dynamic loads which arise at the current high speeds of modern looms. In addition, such a crank lever could not, as is necessary, comprise an annular region at the lever centre of rotation which is sufficiently hard to reduce friction and wear to a minimum, said central annular region having to act both as a rotation bearing and a thrust bearing for adjacent crank levers.